Conventionally, in electrophotography, images are obtained by forming an electrostatic latent image on a photosensitive member by utilizing a photoconductive material and by various means, subsequently developing the electrostatic latent image into a toner image by using a toner, and then transferring the toner image to a transfer material such as paper, followed by fixing by the action of heat, pressure, heat-and-pressure, or solvent vapor.
Usually, in toners used in image formation, a release agent is contained as an additive for achieving an improvement in fixing performance. However, where such a toner containing the release agent is used in an image forming process having a fixing step, the toner comes under conditions where it is exposed to high temperature, and hence any readily volatile component such as a low-molecular weight component contained in the release agent volatilizes to cause a problem that a fixing assembly is contaminated.
Accordingly, a toner is proposed in which the heating loss (volatile loss on heating) of the release agent has been specified (see PTL 1). However, toners used in recent years are often put to fixing at a temperature of 200° C. or less, where the toners by no means come under conditions where they are exposed to a high temperature of 300° C. or more.
Accordingly, a toner is proposed in which the heating loss of the release agent at 200° C. has been specified and further, in order to improve the release properties of the toner, the melt viscosity of the release agent has been controlled (see PTL 2). Studies made by the present inventors, however, have revealed that, in order to satisfy development stability at the time of high-speed printing, there is room for further improvement.